Engine combustion may generate soot, which can be exhausted to the atmosphere. To reduce soot emissions, a particulate filter may be used. To sense the soot produced and/or released, a soot sensor may be used.
Soot sensors may include various types. For example, as described by U.S. Pat. No. 8,310,249, soot sensors collect particles on charged electrodes. In one example, a soot sensing arrangement for includes a pair of spaced apart electrodes having an insulator interposed therebetween, where the first electrode, second electrode and insulator extend into the exhaust flow. As the exhaust flow impinges on the first electrode, second electrode and insulator, any soot or particulate therein can likewise impinge thereon. A voltage supply operably coupled to the first and second electrodes provides a predetermined voltage between the first and second electrodes and a current sensor operably coupled to the first and second electrodes senses current between the first and second electrode. The soot sensor may then be regenerated.
The inventor herein has recognizes disadvantages with the above approach. For example, non-uniform soot deposit on the surface can occur due to bias flow distribution across the sensor surface, resulting in inaccurate voltage and current readings across the gap. Additionally, or alternatively, it can be difficult to reach sensor regeneration temperature due to large flow impingement on the surface in some sensor designs. Further still, contamination may be problematic due to large particulate or water droplet impingement on the sensor surface.
At least some of the above issue may be at least partially addressed by a method, comprising: collecting soot particles on a sensor surface downstream of a particulate filter to increase pressure inside the sensor; and repeatedly regenerating the sensor surface to indicate soot level responsive to a translated piston upon which the pressure acts. In some examples, exhaust exits the sensor via an exhaust outlet that is perpendicular to an exhaust inlet. In this way, it is possible to reduce the effects of biased flow distribution across the sensor while also reducing exhaust cooling effects and large particulate or water droplet impingement. For example, the sensor surface can be positioned perpendicular to the inlet thereby reducing the potential for impingement and uneven exhaust flow. Likewise, by correlating the pressure rise with soot storage, rather than current and/or voltage correlations related to conductivity across a gap or other similar structure, the sensor may be less sensitive to aberrant storage distribution levels on the surface. However, such pressure correlation may also be used in addition to conductivity across electrode gaps, if desired.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.